Venus Express reveals planet's night side

The clouds in Venus's atmosphere behave are more irregular and chaotic on its night side than on its day side, according to a new study.

A mosaic showing the atmospheric super-rotation or the upper clouds of Venus. Right shows the direction of rotation on Venus’s day side, which appears more uniform, while left shows the rotation on the planet’s night side, which is more irregular.
Credit: ESA, JAXA, J. Peralta and R. Hueso


Data from the European Space Agency’s Venus Express mission has been used to study the wind and upper cloud patterns on the night side of Venus for the first time, with surprising results.

A study using data captured by the satellite during its time orbiting the planet reveals that the atmosphere on Venus’s night side behaves more irregularly and chaotically than on the side of the planet facing the Sun.

Venus is a turbulent planet with strong winds that whirl around it, faster than the planet itself rotates.

Its winds rotate up to 60 times faster than the planet below, dragging along clouds as they do so.

This atmospheric circulation had been studied before, but not much was known about Venus’s night side.


Fast filaments in clouds on Venus.
Credit: ESA, S. Naito, R. Hueso and J. Peralta


"We've spent decades studying these super-rotating winds by tracking how the upper clouds move on Venus' dayside. These are clearly visible in images acquired in ultraviolet light," says Javier Peralta of the Japan Aerospace Exploration Agency, an author of the study.

"However, our models of Venus remain unable to reproduce this super-rotation, which clearly indicates that we might be missing some pieces of this puzzle."

Venus Express’s Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) was used to view the clouds in infrared. This created a 'cube' of thousands of images at different wavelengths, revealing phenomena on its night side that have never been seen before on the day side.

Theoretical models for how Venus’s atmosphere behaves predicted the rotation of clouds occuring similar to how it occurs on the day side. But the data shows that the rotation is more irregular and chaotic on the night side.

The clouds form large, wavy and irregular patterns, many of which are not seen in images of the day side of Venus.

"Stationary waves are probably what we'd call gravity waves–in other words, rising waves generated lower in Venus' atmosphere that appear not to move with the planet's rotation," says study co-author Agustin Sánchez-Lavega of University del País Vasco in Bilbao, Spain.

"These waves are concentrated over steep, mountainous areas of Venus; this suggests that the planet's topography is affecting what happens way up above in the clouds."

Carousel image: an artist's impression of Venus Express in orbit around Venus
Credit: ESA
Like this article? Why not:
Boiling exoplanet has titanium atmosphere
previous news Article
Hubble observes 'pitch black' exoplanet
next news Article
We use cookies to improve your experience of our website. Cookies perform functions like recognising you each time you visit and delivering advertising messages that are relevant to you. Read more here